Democrats have spent months praying for the liberal answer to Sheldon Adelson and the Koch brothers.

For the super PAC supporting President Barack Obama, there are plenty of potential recruits who can write multimillion-dollar checks — just few who have stepped forward.

With Republican outside groups on course to raise more than $500 million combined for the cycle, the pro-Obama super PAC Priorities USA Action is finding itself badly outgunned. Mega-donors either say privately they’ve been turned off by the White House’s disdain for outside spending, or by the president’s personal aversion to the constant care and feeding of contributors that such high-profile donors demand, a practice that his two most recent predecessors engaged in with flair.

Liberals have made clear publicly that they don’t approve of the Citizens United Supreme Court ruling that has opened the floodgates to unlimited donations, and a number are refusing to open their wallets to fund pro-Democratic outside groups to voice their opposition to the way politics now works. Some have feared giving large sums might attract media attention — names like Adelson, the Kochs and Texas homebuilder Bob Perry have borne that out. Furthermore, many got the signal for nearly a year from the White House to stay away from Priorities, receiving a different message only when it was clear Democrats would be vastly outraised.

Officials with Priorities refused to comment for or participate in this story.

But, based on a review of past donors and interviews with bundlers and others in Democratic donor circles, here are the top seven pro-Obama families and individuals who could write multimillion-dollar checks to Priorities, but haven’t:

* Penny Pritzker. Of all the people who are avoiding the super PACs this cycle, Pritzker is the most prominent as the former finance chairman of Obama’s 2008 campaign. Pritzker is from a Chicago-based, wealthy business family, and was among those who went out on a limb in the 2008 race by supporting her home state senator.

She is close with Chicago Mayor Rahm Emanuel, the president’s first chief of staff. As of March 2012, she was worth $1.8 billion, according to Forbes. The family acquired its wealth selling assets to the Warren Buffett-operated Berkshire Hathaway, and by creating the Hyatt hotel chain.

Pritzker was described in a CNN story in late 2008 as the president-elect’s top choice for Commerce secretary. But she was ensnared in the subprime lending crisis fallout, thanks to a bank she chaired in Chicago, and labor also waged an offensive against the way Hyatt hotels treats its employees, hitting Pritzker personally.

Pritzker aides did not respond to a request for comment. But Democratic donor sources have said she, like a number of the president’s major contributors, has privately expressed frustration with Obama’s team. She is among those, according to sources, who feels as though she has been slighted by a White House that has little interest in donor maintenance, even to some of its staunchest supporters. She also, according to a recent New York Times piece, has said she dislikes Citizens United.

Nonetheless, Pritzker is in the rarefied group of donors for whom writing a multimillion-dollar check would be quite easy — and, if she decided to donate, it would be a signal to others to do the same.

* George Soros. The Hungarian-born billionaire was ranked fourth on the last Forbes list of the world’s wealthiest people. He was a major donor to the Democratic third-party group ACT in 2004, which raised $137 million for field operations for the Democratic ticket that year to go against the vaunted George W. Bush field machine. A few years later, Soros joined the progressive group Democracy Alliance, a patchwork of groups focused on progressive politics and causes.

But despite those activities, Soros has opted not to give to Priorities. Soros has given $1 million apiece to two groups associated with Democracy Alliance — and that’s it. He remains a symbol of liberal giving for Republicans, yet Adelson on the right is en route to eclipsing him this cycle.

Sources close to Soros say there are a number of reasons for the Democrat’s limited role this cycle, one of which is that 2004 was an unusual cycle in which he saw the Democrats as heavily outmatched in terms of ground game. He also has had little desire, sources said, to contribute to super PACs, which invariably are focused on negative ads (the inherent contradiction here is that one of the groups he’s given to, American Bridge 21st Century, spends its time researching video that gets used in negative ads).

Soros is also not convinced, as one source said, “that even if he gave $500 million, it would be dispositive.” Sources close to Soros suggest it was unrealistic to assume that, just because he gave heavily during one cycle that he would do it indefinitely. But it’s also understandable why Democrats were hoping he would do more.

* The Crown family. In 2008, Lester Crown, a frequent name on the Forbes 400 list and as a member of a prominent Chicago family, made public his preference for Obama as a candidate. He praised the then-senator’s commitment to Israel.

Crown’s daughter, Susan, is a major donor to Mitt Romney this time around. But the family is worth more than $4 billion, and there is room for a split decision.

“We’ve talked about it. It’s an act of conscience for my dad and an act of conscience for me,” Susan Crown told Crain’s Chicago Business. “Reasonable people can disagree and still respect one another.”

Yet that disagreement hasn’t translated into money for Priorities from another wealthy family and longtime supporter of the president who could easily write a large check.

Lester Crown’s major issue is Israel, and it’s unclear if he’s satisfied with Obama on this topic at this point.

In an interview with The Atlantic’s Jeffrey Goldberg in 2010, Crown — who was reportedly asked by an Israeli general to deliver a message to the president to get tougher on Iran — made clear he himself wanted a shift toward a harder-line approach.

“I support the president,” Crown said. “But I wish [administration officials] were a little more outgoing in the way they have talked. I would feel more comfortable if I knew that they had the will to use military force, as a last resort. You cannot threaten someone as a bluff. There has to be a will to do it.”

Also among those missing in action is Lester’s son, James, who raised $500,000 for the president’s 2008 race, but hasn’t given anything this time.

Aides to the Crowns did not respond to a request for comment.

* Peter Lewis. Like Soros, the Progressive Insurance chairman was a major donor to ACT in 2004, and a Democracy Alliance member for years, from its inception in 2005.

In March, Lewis formally, but quietly, parted ways with the donor network, a clear signal he didn’t plan a repeat of his 2004 giving level, when he donated $25 million. He has also shunned super PACs, over the same concerns other Democratic-leaning donors have voiced over the impact of Citizens United on the process.

In an email to POLITICO, Jennifer Frutchy, a Lewis adviser, said: “He made a personal decision after spending tens of millions of dollars on the 2004 election not to spend his funds on advertising, preferring to build the progressive infrastructure — the think tanks, media monitoring, leadership training, etc. That is where his focus has been and continues to be. He finds the corrupting use of money offensive with its negativity and denigration of opponents. He does not want to be part of corrupting the electoral process any more than it already is. He gave only to American Bridge for its start-up in 2011, which is for research, rather than campaign advertising. He currently has no plans to give to super PACs.”

Bluhm hosted the president’s 49th birthday, where the asking price was more than $30,000-a-head, with the cash going to the Democratic National Committee. But he has also been silent as far as Priorities goes.

His absence has been noted — when Bill Clinton was asked to attract donors for Priorities a few months back, the response from the former president’s longtime supporters was the logical one — that they wanted the current president’s friends to donate first.

* Warren Buffett. The Oracle of Omaha made clear in May that, on principle, he has no plans to help Priorities USA Action.

“I don’t want to see democracy go in that direction,” Buffett was quoted by Bloomberg News telling his annual Berkshire Hathaway shareholders meeting. “You have to take a stand some place.”

Keeping a fat wallet closed, Buffett is the embodiment of liberal disgust with the campaign finance system. He’s worth more than $44 billion, and has made clear how much he wants to see Obama reelected. But, like Soros, he believes the Citizens United ruling was a blow to the nation, and not one he wants to abet.

Nonetheless, Democrats had been hoping for months that the man for whom Obama named a tax proposal aimed at top earners would be persuaded to help Priorities keep pace with the other side.

* Eric Schmidt. The Google executive chairman’s worth is estimated at $7 billion by Forbes, and he has been a major donor and campaign adviser to Obama. He was reportedly a Commerce secretary contender at one point in late 2008, and served on the president’s transition advisory board.

In terms of contributions to his Obama’s campaign committee, Schmidt has maxed out to the president this cycle, and has made clear where his support lies. But, like other would-be big Democratic donors, he is not helping out a super PAC.

Schmidt is a representative of the burgeoning tech field that has money to spare, and is a prime source for new political donations. But what’s striking about Schmidt is he has been cited as having a major impact on Obama’s team.

In a recent Bloomberg News profile on Obama campaign manager Jim Messina, he was named a key influence.

“Jim and I met in the 2008 campaign and just hit it off on a personal basis,” Schmidt said in the piece, in which he was named as helping set up meetings with CEOs for the campaign. “We became very good friends.”

* Tim Gill. The LGBT activist and Quark Inc. software maverick is not possessed of the same level of wealth as others on this list. But he is a multimillionaire who has been generous with causes he cares about. One of them has been the fight to legalize gay marriage.

When Obama said publicly that he believes that people of the same gender should be allowed to marry, the assumption was that a number of prominent gay donors, who had floated in the press that they were holding back their contributions until the president said where he stood on the issue, would vote with their wallets through Priorities.

That has not happened yet. While Gill, whose aides didn’t respond to a request for comment, is by no means the only wealthy and influential gay donor who cares about this issue, he is among the best known.